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Chem 202 > Lab Final > Flashcards

Lab Final Flashcards

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1
Q

Green chemistry

A

an approach to chemistry that aims to maximize efficiency and minimize hazardous effects on the environment and human health

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2
Q

Where do Emory shuttles get fuel for shuttles?

A

160 tons of fryer oil and grease were collected in 2017 and made into biofuel for Emory’s shuttles

*uses B5

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3
Q

Why is B80 used in the cold instead of B100?

A

Diesel is more viscous so it makes more sense to use a lesser proportion of biodiesel when it is cold

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4
Q

Chemical composition of fatty acids

A

RC(=O)OH

R: long chain hydrocarbon

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5
Q

Why can you not just use animal fats as fuel?

A

They are solids or viscous at room temperature (saturated fats)

Need to make able to flow

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6
Q

Unsaturated fatty acids

A

long chains that contain a C=C double bond

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7
Q

Is anything a pure saturated fat?

A

Rarely and the kinks make it difficult to pack triglycerides

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8
Q

What is the red diamond in old hazard label?

A

Flammability

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9
Q

What is the blue diamond in old hazard label?

A

Health

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10
Q

What is the white diamond in old hazard label?

A

Special notice

ex: reacts with water in unstable manner

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11
Q

What is the yellow diamond in old hazard?

A

Instability/reactivity

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12
Q

Comparison of butanol vs. ethanol as fuel

A

Butanol has more carbon chains so more energy produced

Ethanol produces more CO2

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13
Q

What was our biodiesel?

A

a methyl-ester

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14
Q

Difference between temperature and heat?

A

Temperature is a measure of molecular motion or kinetic energy

Heat is a transfer of thermal energy between two objects due to differences in temperatures

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15
Q

Intermolecular forces in methanol

A

hydrogen bonding (oxygen)

dipole-dipole

dispersion

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16
Q

Intermolecular forces in canola oil

A

mostly dispersion

some dipole-dipole due to ester groups

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17
Q

Heat of combustion units

A

kJ/g

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18
Q

How to find heat of combustion?

A

Normally take how many kJ to heat water and divide by grams of biodiesel, etc.

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19
Q

Why is biodiesel said to be carbon-neutral although it produces CO2?

A

Since biodiesel is made from rapeseed and not fossil fuels, it is said that the carbon the rapeseed absorbs during its lifetime is equal to the CO2 released

no net addition to the atmosphere

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20
Q

Why is the methanol and the canola oil able to mix?

A

the canola oil contains an ester bond that makes it slightly polarized

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21
Q

Why is biodiesel less viscous than starting triglyceride?

A

it is a smaller molecule

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22
Q

Kinetics

A

applies to the SPEED of a reaction

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23
Q

Thermodynamics

A

applies to the EXTENT of a reaction, the concentration of product that has appeared after an unlimited time

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24
Q

Fetal hemoglobin

A

More efficient at binding O2

Has a larger K value

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25
Q

Beer-lambert equation

A

A = elc

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26
Q

Molar absorbitivity constant

A

e in Beer’s Lambert equation

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27
Q

3 ways to stress a system

A
  1. Temperature
  2. Concentration
  3. Pressure
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28
Q

How do you measure concentration through absorbance when equilibrium is dynamic (i.e. there will never be purely products)?

A

Put in so much of one of the reactants so that the system is essentially driven to completion

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29
Q

How do you determine the wavelength to set spectrometer to for an unknown compound?

A

Look at the peaks of absorbance on scanning setting

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30
Q

What should you use as your blank to measure concentration of FeSCN2+ ?

A

Highest concentration of iron

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31
Q

What should you do to calculate concentration when not given much information?

A

M1V1=M2V2

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32
Q

What happens to the amount of acid when base is added?

A

Amount of acid decreases

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33
Q

How to calculate enthalpy when K was calculated at 2 different temperatures?

A

Van Hoff’s Equation

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34
Q

What is the gas constant, R?

A

.008314 kJ/mol

or

8.314 J/mol

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35
Q

What happens when you add silver nitrate to an anion?

A

Often makes a white precipitate

Ag(anion)

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36
Q

What is borax?

A

a slightly soluble salt

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37
Q

How to determine K when there are two products?

Formula looks like: K = [A]2[B]

A

Can use the mol ratio to substitute

Know that for every 1 mol B, there are 2 mols A

K = [A]2[2A]

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38
Q

How can we calculate K by titration?

A

use the known concentration of the acid/base to solve for the concentration we are looking for

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39
Q

End point

A

is when the color changes, indicating the end of the titrant

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40
Q

Equivalence point

A

when the number of moles of acid is equal to the number of moles of base

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41
Q

Titration using a mass burette vs. titration using a volumetric burette

A

same calculations except one using volume and the other uses mass

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42
Q

Why do we use different indicators?

A

Different indicators are sensitive to different pHs

Phenol red is sensitive to ~7
Phenophtalein is sensitive to ~9

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43
Q

How do you determine the temperature of a solution if you have to measure its absorbance?

A

measure the temperature before and after sampling in the spectrometer

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44
Q

Why does it not matter how much water is used to move a sample to a flask for titration?

A

the number of moles of the substance studied will remain the same

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45
Q

Why do we not use M1V2=M1V2 with the acid and base for a titration?

A

This assumes that there is a 1:1 mol ratio between the acid and base which we do not know

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46
Q

Amount of titrant needed when solubility increases?

A

Less soluble = less titrant

More soluble = more titrant

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47
Q

What are the units of entropy?

A

J/K

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48
Q

What happens if extra borax was transferred to the flask for titration?

A

more borate = larger K

larger K = less free energy, since G=-RTln(K)

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49
Q

Where is the buffer region of a titration curve?

A

the flat line leading up to the spike to the equivalence point

at this point there is conjugate acid and conjugate base present

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50
Q

If you titrate a weak acid with a strong base, what is true of the equivalence point?

A

all of the weak acid would have been converted to conjugate base

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51
Q

What is true of halfway to the equivalence point?

A

there are equal amounts of conjugate acid and base

use Henderson-Hasselbach equation…you have a buffer!!

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52
Q

Why does Ka decrease as starting pH increases of a titration?

A

a higher starting pH indicates a weaker acid and therefore it is not as reactive

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53
Q

Rate of reaction

A

speed at which reactants are converted into products

M/s

kinetics

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54
Q

What is the central focus of chemical kinetics?

A

reaction rates

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55
Q

If given a graph of concentration vs. time, how do you find the reaction rate?

A

take the slope

rate = d(concentration)/dt

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56
Q

What would result in the rate change being a decrease by a factor of 4?

A

A reaction is second order with respect to reactant B and B is halved

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57
Q

5 factors that affect rate

A
  1. Nature of reactants
  2. Temperature
  3. Catalyst
  4. Concentration of reactants
  5. surface area of reactants
58
Q

Effect of surface area on concentration

A

Greater the surface area, the faster rate of reaction

More particles are exposed to attack by other reactant particles

59
Q

Arrhenius plot

A

ln(k) vs. 1/T

  • use slope to calculate activation energy
  • use y-intercept to calculate A
60
Q

How do catalysts work?

A

New mechanism

Lowers activation energy (resulting increases k)

They increase the rate of both the forward and the reverse reactions

61
Q

Relationship between activation energy and k

A

inverse relationship

62
Q

Relationship between temperature and k

A

direct relationship

63
Q

Surface catalyst

A

a solid that speeds up a reaction between gases

64
Q

What is slope in a first order reaction plot of ln(A) versus time?

A

slope = -k

65
Q

What is slope in a second order reaction plot of 1/A versus time?

A

slope = k

66
Q

What is slope in a zero order reaction plot of A versus time?

A

slope = -k

67
Q

How to determine the reaction order by graphing?

A

Graph A vs. t, ln(A) vs. t, and 1/A vs. t

  • each correspond to a different order respectively
  • known as integrated rate laws
68
Q

What is the limitation of the integrated rate laws?

A

Can only work for a single variable

69
Q

How to rearrange pseudo-rate laws?

A

flood the system with A, so there is basically no change in A

rate = ko [B]^n

70
Q

What does K observed equal?

A

ko = K[A]^m

*A is what the system was flooded with

71
Q

Beer’s Law Plot

A

Absorbance vs. Concentration

72
Q

How to determine the molar absorbvitity constant?

A

use the slope of the Beer’s plot

73
Q

Redox process in ionic compounds

A

there is a complete change in electrons

74
Q

Redox process in covalent compounds

A

there is a shift in electrons

75
Q

Oxidizing agent

A

is reduced

gains electrons

76
Q

Reducing agent

A

is oxidized

looses electrons

77
Q

Oxidation number

A

a number assigned to a chemical that represents the number of electrons gained or lost (if the number is -)

78
Q

Electromotive force

A

E cell

the cell voltage or cell potential

*can occur due to flow of electrons between the anode and cathode

79
Q

Anode

A

where oxidation occurs (loosing electrons)

is denoted on the left in a standard diagram

80
Q

Cathode

A

where reduction occurs (gaining electrons)

is denoted on the right in a standard diagram

81
Q

Galvanic or voltaic cells

A

produce electricity as a result of spontaneous reactions

82
Q

Electrolytic cells

A

non-spontaneous chemical change driven by electricity

83
Q

An Ox and a Red Cat

A

An Ox: anode = oxidation

Red Cat: cathode = reduction

84
Q

Cats are +

A

Cathode is positive

85
Q

Why does a voltaic cell work?

A

the spontaneous reaction occurs as a result of different abilities of materials to give up their electrons

86
Q

Cell voltages

A

the potential differences between the electrodes

87
Q

The Standard Hydrogen Electrode

A

an arbitrary 0 chosen to compare potentials of individual electrodes

88
Q

Colors of Manganese in Different Oxidation States

A 
\+7 = magneta
\+6=green (Arnold)
\+5=yellow (or blue) (Tina)
\+4=clear w/ brown precipitate
\+3=pink
\+2=clear w/ no precipitate
89
Q

What is the relationship between oxidation number and reducing ability?

A

greater oxidation number = greater reducing agent

a higher oxidation number means that it lost the most electrons, which means that it donated the most to another substance. it did the most reducing

90
Q

When can you compare oxidation number and reducing ability of different substances?

A

they have to be reducing the same substance

91
Q

What happens if two samples are contaminated in the murder mystery experiment?

A

the stronger reducing agent (higher oxidation number) will mask the color of the weaker reducing agent

the stronger reducing agent is more reactive

92
Q

Ferromagnetic electron spin

A

unpaired electron spins from the atoms in the solid (represented by arrows) align with each other within regions called magnetic domains

93
Q

Ferrimagnetic electron spin

A

within each magnetic there are two spins in different directions

However, they do not cancel out and this leaves a net magnetism

94
Q

Did we use a ferromagnetic or ferrimagnetic substance?

A

Magnetite is a ferrimagnetic substance

95
Q

Superparamagnetic

A

the magnetic domains are the particles themselves

all the electrons within a given particular spin in the same direction

*ferrofluids are superparamagnetic and this makes them magnetize and demagnetize more rapidly

96
Q

Why do ferrofluids form peaks?

A

they are part of a colloidal suspension that always has small waves constantly present on the surface of a ferrofluid

these waves are amplified in the presence of a magnetic field

97
Q

Reaction mechanisms definition

A

a step-by-step description of actual events (often collisions) in an overall chemical reaction

98
Q

What does every step of a reaction mechanism do?

A

Alters a molecules geometry, energy, or produces a new molecule

99
Q

Why do trimolecular processes rarely occur?

A

the probability of 3 molecules colliding at the same time is incredibly rare

100
Q

Order in a rate law for an elementary process

A

are the same as the stoichiometric coefficients for an elementary process

101
Q

Intermediates

A

produced in one step and consumed in another

102
Q

Rate determining step

A

one elementary step is usually slower than all others

103
Q

SN1 mechanism

A

2 step mechanism

produces an intermediate

1st order reaction

104
Q

SN2 mechanism

A

1 step mechanism

does not have an intermediate

2nd order reaction

105
Q

Chemical formula of magnetite

A

Fe3O4

106
Q

Suspension

A

a heterogenous mixture that has solid particles large enough to settle to the bottom

107
Q

Colloid

A

a solution that has evenly distributed particles large enough to remain suspended, but do not settle to the bottom

108
Q

Surfactant

A

a compound that is added to a liquid to lower its surface tension

ex: detergents

109
Q

Hydracids

A

an acid that does not contain an oxygen

composed of hydrogen and a nonmetallic element

ex: HF

110
Q

Solvolysis Reaction

A

a substitution reaction where the solvent is a nucleophile

111
Q

Why is a surfactant used in making your ferrofluid?

A

a surfactant prevents the particles of magnetite from clumping together (agglomerating)

can’t have agglomeration because they need to be equally suspended throughout the solution

112
Q

Why are Fe(ii) and Fe(iii) not magnetic?

A

their electrons move independently of one another and do not contain large regions where the electron spins are alligned

113
Q

In the SN1 reaction experiment, what were the controls? What did they control for?

A
  1. Not heated test tube. Controlled for tert-butyl’s natural reaction with ethanol without heating.
  2. No alykl halide added. Controlled for the heating effects of ethanol and the indicator
114
Q

3 alkyl halides reactivity with ethanol

A

3º, 2º, 1º

*decreasing order. 3º is the most reactive

115
Q

Why did only tert-butyl react with the AgNO3?

A

tert-butyl has an SN1 mechanism, so when the carbocation intermediate is formed, there is a free halide to combine with the silver and form a precipitate

116
Q

3 steps of SN1 reaction

A
  1. Formation of carbocation
  2. Nucleophilic addition of alcohol
  3. Deprotonate by solvent
117
Q

Why is tert-butyl the most reactive with ethanol

A

It has a carbocation intermediate that is highly unstable

118
Q

What happens within the atom when it is fluorescing?

A

Atom gets excited to a higher energy level and then it emits light when it falls from these higher energy levels

119
Q

Who was awarded the nobel prize in chemistry 2008?

A

Martin Chalfie, Osamu Shimomura, Roger Y. Tsien

120
Q

How are GFPs used in biology?

A

can be attached to proteins to see if gene splicing/gene expression worked

121
Q

What did Roger Tsien do?

A

changed the structure of GFP to produce proteins that glowed cyan, blue, and yellow

122
Q

What did Martin Chalfie do?

A

used GFP to label neurons in C. elegans

123
Q

Who was the first genetically modified primate?

A

ANDi

statistically very hard to accomplish

124
Q

What is the structure of GFP?

A

green flourescent protein consists of 238 amino acids folded in the shape of a beer can

the ends of the chain interact in the middle to create the light (chromophore)

125
Q

Fluorescence

A

lumination that is due to quickly absorbing high energy light and releasing two or more photons

126
Q

Phosphoresence

A

lumination that occurs more slowly over time

127
Q

Coordination number

A

the number of ligand atoms that are bonded directly to the central metal ion

128
Q

Geometry

A

the geometry (shape) of a complex ion depends on the coordination number and nature of the metal ion

129
Q

Ligand atoms

A

an ion or molecule that binds to a central ion in order to form a coordination complex

130
Q

Donor atoms per ligand

A

molecules and/or anions with one or more donor atoms that each donate a lone pair of electrons to the metal ion to form a covalent bond.

131
Q

What properties do ligands have?

A

they are lewis bases

they are able to donate a pair of electrons

132
Q

Monodentate ligands

A

use one pair of electrons to form one point of attachment to the metal ion

133
Q

Bidentate ligands

A

use two pairs of electrons to form two points of attachment with the metal ion

*can go up to tetradentate, etc.

134
Q

Asymmetric synthesis and when it is utlized

A

using chiral reagents, catalysts, and fragments to produce SINGLE enantiomeric configuration

this approach is used when dealing with big biomolecules

135
Q

Chromatographic resolution of enantiomers

A

requires an optically active (chiral) stationary phase that allows passage of one enantiomer while the other is held up on the column.

applicable when dealing with a small amount of material

136
Q

Resolution by crystallization

A

*what we did

diastereomer formation followed by product enrichment by the selective crystallization of one diastereomer over the other.

137
Q

What is the blank for the polarimeter?

A

Water

138
Q

What does Co(en)3 represent?

A

C6 H24 N6 Co

139
Q

What is the purpose of a solvent/moisture trap in a vacuum filtration?

A

Capture solvent that could have been sucked into the line, so the solvent does not destroy the pump

140
Q

What is the purpose of hydrogen peroxide in the preparation of Co(en)3 3+?

A

hydrogen peroxide works as a oxidizing agent

oxidizing Co(ii) to Co(iii)

141
Q

two major safety hazards of the first experiment?

A

not to come into contact with sodium hydroxide and hydrogen peroxide

142
Q

After the (+) enantiomer was isolated, why did you have to precipitate the iodide salt out of it?

A

If we dissolved the crystals into the solution, we would have had additional molecules that can rotate light, so we had to isolate the Cobalt from the tartrate

Chem 202 (7 decks)

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